This invention relates to magnetic recording media such as tape, and more specifically to a method of producing a magnetic coating material for the recording media which is highly effective in reducing the electric resistances of the media and in avoiding various troubles which would otherwise result from static charge accumulation.
With adsorption of dust on its coating, the magnetic recording tape tends to develop troubles, e.g., dropouts and reductions in level due to choking of the head. The attraction of dust is ascribable to the buildup of static charge on the magnetic recording tape with frictional electricity produced as the tape runs in sliding contact with the guides, head, and associated parts of the recorder. In extreme cases it can cause a discharge noise.
Attempts to preclude such troubles have been made, including the incorporation of antistatic agents into or over the magnetic coating films, and addition of carbon black or metal powder to the coatings. However, those methods hitherto proposed have had one drawback or another. For example, the addition of the antistatic agents can cause blooming or degradation with the elapse of time. When carbon black or metal powder is used, tendencies toward low sensitivity and deterioration of the coated film are frequent problems. With metal powder in particular, these problems are pointed up because of the surface oxidation with air and a sufficiently large amount to make up for the loss must be used if an adequate antistatic effect is to be achieved.